A major concern at every stage in the manufacture of electronic components is contamination. Control of contamination is critical to product quality, and an extremely high level of cleanliness and purity in the manufacturing environment is needed for obtaining acceptable product yield and maintaining profitability. These requirements are particularly acute in the manufacture of very high density circuitry as well as in ultra-precision bearings, recording heads and LCD displays.
Sources of contamination include the manufacturing facility, personnel and processing equipment. In many cases, contamination can be lowered to acceptable levels by the use of "clean room" techniques such as isolation, air filtration, special equipment and special clothing and body coverings to avoid contact between the operator and the manufacturing materials. With ultra-high precision manufacturing, the highest levels at which defects can be tolerated are particularly low and control over sources of contamination is even more critical.
A problematic source of contamination in ultra-high precision manufacturing is the liquid chemicals used in the manufacturing process. Cleaning and etching agents and other treatment chemicals must be extremely pure and free of particulate matter to produce acceptable product in high yield. Chemicals brought in from outside sources, however, contain inherent contamination which they bring to the manufacturing area. Contamination is contributed by the preparation of the chemicals, the packaging in which the chemicals are shipped as well as the packaging operation, the handling the chemicals receive during transfer from the manufacturer, and decay of the chemicals in the packaging during shipment or storage.
Further difficulties arise in those procedures which require treatment chemicals which do not meet Department of Transportation regulations, and therefore cannot be shipped in a manner which requires conformance with these regulations Examples are nitric acid at concentrations exceeding 70%, high-purity oleum, ammonium hydroxide at concentrations exceeding 28%, and hydrogen peroxide without stabilizers.
Clearly there is a need for a reliable means of supplying these treatment chemicals at a purity level which will produce a high yield of acceptable product in ultra-high precision components, and which can meet the requirements of advancing electronics technology.